Being responsible and checking with support if a certain thingy is even supported before ordering a new vps is boooooring!! (Esp when you send in the question at just about EoB..)
What are even the odds that an x86 vps doesn't support SSE4 in this day and age? But then again, LSE for ARM CPUs came in 2018 and is not supported..... (Think I know how netcup is so cheap, and why they don't have more hardware specs available on their homepage ​​)
Something else is going on here, I think.. Probably something to do with how the VPSs are provided, virtualisation etcetc, stuff I know almost nothing about.. :P

Just checked on the ARM VPS I have (still no answer from support..), and it is running on an ARM Neoverse-N1, which has the flag "atomics", indicating support for LSE. But if I do a
cat /proc/cpuinfo, it doesn't have the flag "LSE" (which is where you should look according to GTS's docs whether or not you can install the proper version or the experimental, unsupported one..)
Considering just getting an x86 vps and check since support is so slow..... ​​ But I really don't want to reward them for being slow..