The ATESH group quoted does have a wiki.
Described as a group of Ukrainians and “Crimean Tatars” in their own wiki. The article calls it a Russian partisan group.
The group says a goal is to have the Ukraine Constitution modified to declare Crimea an autonomous National Republic.
All of their claimed actions take place in Crimea and southern Ukraine via what is quoted as “1000 Tatars”. Not clear how that translates to “Russian partisan group”.
2014 Census of Crimea (over 2 million people) lists Tatars at 12%, Russia at 68% and Ukrainians at 16%. 2021 lists no change in Tatar population, Ukrainians left and down to 7% and Russians now 76%. Tatars were dominant % up to the mid 1800s and then via various causes they disappeared from significance.