Have you looked at Node.js backend jobs? Maybe try and take a full stack job where you do both FE and backend and slowly transition to more backend work?
It worked for me. FE JS -> Fullstack JS -> Backend Node.js.
It can take time, I was probably 2-4 years in each, required some study, and some interviews didn't work out for experience reasons, some did because I could prove I understood the issues at hand.
I'm now firmly in Desktop/Embedded which comes with its own challenges, but could not be happier about escaping JS and its... Oddness.
FE JS -> Fullstack JS -> Backend Node.js. -> Backend Python/Lua/C -> Desktop Software -> Embedded Software
It can take time, I was probably 2-4 years in each, required some study, and some interviews didn't work out for experience reasons, some did because I could prove I understood the issues at hand.
I'm now firmly in Desktop/Embedded which comes with its own challenges, but could not be happier about escaping JS and its... Oddness.