embix

Just rewrite it with 80% functionality and force migrations on the users. Once the remaining 20% “edge cases” that require serious effort hop to the next job - where you where hired to “maintain” such a system and “just add a small feature here and there”. Ooops.

all other employers demand modern technologies

There are a lot of employers that’ll throw good money at you for maintaining and extending their outdated crap. Have you ever considered learning COBOL?