As an alternative to #395 and #236 that doesn't require porting some other crypto library like WolfSSL to Vintage Windows, refactoring PuTTYs plink into an SSH backend for Kermit 95 may be a not unreasonable option for getting SSH support back on Windows 95 and NT 4.0, and its perhaps the best option for getting something going on RISC NT given PuTTY already supports the required compiler (Visual C++ 4.0) and has been built for those platforms in the past.

The main downside for this is it wouldn't help with OS/2 support, and it would probably be a bit of a maintenance burden having to effectively keep a modified fork of PuTTY up-to-date. But I think some other projects effectively do just that (TeraTerm perhaps?).