The "kernel too old" error means what it says: the Linux kernel you are using is too old to run usearch. If you have paid for a 64-bit license and want to run your 64-bit binary on an old version of the kernel, then I will try to find a solution for your particular case if I can. If you want to run a 32-bit binary, then regrettably I can't provide a build for you unless you are willing to pay for my time to do a custom port to your platform.
I take compatibility seriously -- it is important to me that usearch runs on as many platforms as possible. Installing command-line bioinformatics software is often a complex and frustrating process, and I've tried very hard to avoid these problems.
I've spent many hours on the "kernel too old" issue, and unfortunately, it seems that there is no practical way for me, with my limited resources, to make a binary (or small set of binaries) which is both forwards- and backwards-compatible with the full range of Linux kernel versions that are deployed out there.
As best I can determine, this is a new issue that arose
with recent releases of the kernel and gcc compiler libraries. I can solve it on
a case-by-case basis by doing a custom build, but I can't do that for hundreds
of users, especially considering that usearch evolves quickly with new versions
posted every few weeks. If you have a paid 64-bit license, then I will try to
find a solution for you, but I've reluctantly decided to give up as far as the
free 32-bit version is concerned. I think you'll find that a kernel which is old
enough to have this issue with usearch is going to have issues with other tools
as well, so it might be time to consider updating your o/s.