Came from 29.12.20 - umi + littleturtle twrp (we all know the fastboot boot problems and like impatience can be a problem here , haha) been there done that
1. backup (not with twrp) - just safed everthing on pc
2. got newest twrp from MB - big kudos there
3. booted to recovery (littleturtle)
4...