You’re in luck because the C414 and Beaver are 2 aircraft that can have their liveries converted for 2024.
I created a guide for converting liveries for 2020 legacy aircraft in in the link below. I have successfully converted all my 414 liveries using this method.
It’s quite detailed but basically you just make sure your ui_createdby value matches your source aircraft, then dump it in your community folder and it should work. If you want to disable the dynamic tail number, or create some 2024 style thumbnails, then that is more complicated, but covered by the guide. Once finished your C414 liveries should work in both 2020 and 2024.
The Beaver is more difficult as it has been converted to the 2024 format, unlike the C414 there converted livery will only work in 2024. Luckily the Beaver wasn’t done by Asobo so all the textures still work. You just need to use the new folder structure and convert the textures to KTX2 format. I haven’t documented this process, but have successfully converted a few of my Beaver liveries for 2024. Have a look at one I have converted for the folder structure needed.
https://flightsim.to/file/85489/2024-dhc2-beaver-c-gzbe
Just convert all your textures to PNG format and then use this utility to convert the PNG textures to KTX2 format.
If you get stuck, then send me a direct message and I’ll help out.