Scythians were not Turks, they were a separate ethnic group which spoke the Scythian languages. which are part of the Eastern Iranian Subdivision of the Indo-Iranian language family. They lived from what is now Ukraine all the way to the border of the Tarim basin (where the Uyghurs live) The only remaining Scythian language currently spoken is Ossetian. Which is located in the central Caucasus.[1] It is worthwhile noting however, that the term "Scythian" in late antiquity had become genericized among Roman scholars to refer to any people living on the Caspian Pontic Steppe, including the Goths (a Germanic people probably originating in Scandinavia) and the Huns.

With the Huns it is important to note the multi ethnic nature of the steppe empire. The steppe has always been an extremely dynamic place of multi-ethnic tribal confederations of multiple ethnicities and languages. The vast majority of the citizens and soldiers of the Hunnic empire were not of Hunnic origin, and therefore it is difficult to determine the identity of the founding ethnic group. We also only have 3 Hunnic words from 2 passages, which shall be quoted below

"When the Huns had mourned him [Attila] with such lamentations, a strava, as they call it, was celebrated over his tomb with great revelling" -Jordanes The Origin and Deeds of the Goths

"In the villages we were supplied with food - millet instead of corn - and medos as the natives call it. The attendants who followed us received millet and a drink of barley, which the barbarians call kamos" - Priscus (I have unable to locate the fragment but it is quoted in a variety of academic sources).

Both sourced from [2] on pages 424 and 425

None of these words are particularly diagnostic beyond Indo- European, and with a possibility of these words being borrowed from other peoples the Huns encountered.

One more promising lead is that Huns practiced circular cranial deformation. Similar to some Indigenous Andeans, where the head of an infant is bound tightly and the skull is forced to elongate.[3] Various forms of head binding had been used on the steppe prior to 200 AD but were not widespread and not sharing a common origin. The origin of the particular hunnic practice appears to derive from somewhere in central Asia, and then spreads as far west as France in the mid 400's AD as a status of prestige among Germanic tribesmen after the Hunnic conquest. According to [3] "Nearly 80% of the steppe population, which consisted of nomadic societies of different ethnicities, came to shape their heads in the same manner soon after the Hun expansion" The practice was also known among the Alans. (the people who would give rise to the Ossetians)

Another promising lead is the names of the leaders of the Huns which are in order as follows: Balamber, Uldin, Charaton, Octar, Rugila, Bleda, Atilla, Ellac, Dengizich, Ernak. Most of these names appear to derive from Turco-Mongol terms [4] and this reflects current scholarship [5] Meaning that a Turkic ethnicity is likely for the core Hunnic group. As an aside, if the Hunnic language is Turkic it is of uncertain placement in the Turkic language family due to the extremely limited source material but it has limited indications that it might be closer to Bulgar, today known as Chuvash (all other Turkic languages are more closely related to each other than they are to Bulgar) but this is massive speculation based on extremely limited data.

In conclusion, the Scythians aren't Turkish, they're of Iranic origin. The core group of the Huns is probably of Turkic origin, though with uncertain placement among other Turkic languages

Sources:

[1] One Europe, Many Nations: A Historical Dictionary of European National Groups. James Minahan 2000

[2] The World of the Huns: Studies in Their History and Culture. Maenchen-Helfen, Otto J. 1973

[3] Cranial vault modification as a cultural artifact: a comparison of the Eurasian steppes and the Andes . Torres-Rouff, Yablonsky 2005

[4] The Hunnic Language of the Attila Clan. Pritsak, Omeljan 1982

[5] The Huns, Rome and the Birth of Europe. Hyun Jin Kim 2013

Scythians is a general blanket term, but it was mostly used to refer to eastern Iranians like those ancestral to modern-day Pashtuns, Ossetians, and Tajiks.

The Turkic peoples were likely already in close contact with eastern Iranian and other Indo-Europeans during the onset of the Turkic migrations. Areas like modern-day Kazakhstan, the Russian steppe, Turkmenistan, Uzbekstan, Xinjiang (China), and other swaths of Central Asia were inhabited by groups dubbed Scythians at various points, and these areas were all formerly inhabited by west Eurasian Indo-European eastern Iranians, Tocharians, and other Indo-European groups prior to their Turkification by the migrating Turkic tribes.

The Turkic tribes from their homeland in southern Siberia/northern China and areas of Mongolia migrated southward and eastward, coming into direct contact with Indo-European populations, gradually assimilating and admixing with Scythians as they migrated onwards, increasing the "West Eurasian" genetic component (they were most likely mostly "East Eurasian' prior to the migrations, similar in ancestral and genetic makeup to Mongolians).

As such, large numbers of Scythians (eastern Iranians) from eastern China to the Ural steppe were assimilated and Turkified by the Turkic tribes, and modern-day Kazakhs, Turkmen, Uyghers, and Turks all have varying degrees of significant to dominant Scythian (eastern Iranian) ancestry.

Genetically, ancient Scythians samples from Russia were dominantly West Eurasian and related to modern-day Persians, Afghans like Pashtuns (who were refered to as "Saka", or Scythians), and Tajiks, groups who all (except the Persians) have been called Scythians and who descend from these ancient Scythians. Early Slavic speakers have also assimilated alot of Scythian populations, and as such Russians, Poles, and other Slavic groups in Eastern Europe have significant ancestry and genetic ties to contemporary eastern Iranian populations.

The Huns may have been a conglomeration of Turkic, Mongolic, and Indo-European and possibly even Tungusic and Uralic populations, or they may have been Turkic or Turko-Mongolic. It is undecided as of now, but their origins are most likely in the vincity pre-migration Turkic and Mongolic tribes, but their exact compostion as to whether they were a confederation of different population groups or simply a Turkic population or a Turkic-influenced Uralic population like the Magyars (Hungarians) is hard to tell. But from what little evidence and knowledge of Huns we have, a Turkic identity is most likely.