I am clueless wrt .NET, so I'm not sure how feasible an aarch64 build is.  Attempting to use the .NET SDK available via DNF I get:

18:30:48 | andymandias@xvx-016rn:~/D/C/Celeste64 > dotnet --version
8.0.101
18:35:01 | andymandias@xvx-016rn:~/D/C/Celeste64 > dotnet restore
  Determining projects to restore...
  All projects are up-to-date for restore.
18:35:04 | andymandias@xvx-016rn:~/D/C/Celeste64 > dotnet run
Celeste 64 v.1.0.1
Foster: v0.1.14
Platform: Fedora Linux Asahi Remix 39 (Thirty Nine) (Arm64)
Framework: .NET 8.0.1
System.DllNotFoundException: Unable to load shared library 'FosterPlatform' or one of its dependencies. In order to help diagnose loading problems, consider using a tool like strace. If you're using glibc, consider setting the LD_DEBUG environment variable: 
/usr/lib64/dotnet/shared/Microsoft.NETCore.App/8.0.1/FosterPlatform.so: cannot open shared object file: No such file or directory
/home/andymandias/Developer/Celeste/Celeste64/bin/Debug/net8.0/FosterPlatform.so: cannot open shared object file: No such file or directory
/usr/lib64/dotnet/shared/Microsoft.NETCore.App/8.0.1/libFosterPlatform.so: cannot open shared object file: No such file or directory
/home/andymandias/Developer/Celeste/Celeste64/bin/Debug/net8.0/libFosterPlatform.so: cannot open shared object file: No such file or directory
/usr/lib64/dotnet/shared/Microsoft.NETCore.App/8.0.1/FosterPlatform: cannot open shared object file: No such file or directory
/home/andymandias/Developer/Celeste/Celeste64/bin/Debug/net8.0/FosterPlatform: cannot open shared object file: No such file or directory
/usr/lib64/dotnet/shared/Microsoft.NETCore.App/8.0.1/libFosterPlatform: cannot open shared object file: No such file or directory
/home/andymandias/Developer/Celeste/Celeste64/bin/Debug/net8.0/libFosterPlatform: cannot open shared object file: No such file or directory
   at Foster.Framework.Platform.FosterStartup(FosterDesc desc)
   at Foster.Framework.App.Run(String applicationName, Int32 width, Int32 height, Boolean fullscreen)
   at Foster.Framework.App.Run[T](String applicationName, Int32 width, Int32 height, Boolean fullscreen)
   at Celeste64.Program.Main(String[] args) in /home/andymandias/Developer/Celeste/Celeste64/Source/Program.cs:line 25

i think foster (the engine) is mostly c, youd need to compile that seperately and put the libs in the places its expecting.

https://github.com/FosterFramework/Foster/tree/main/Platform

peep this, if you have trouble i can help debug later.

Just want to confirm that it plays well (not just launches well).  Thanks again Anumania!

Edit (x2): Official support is here :)  Removing a now-dead link to no-longer-necessary explicit build steps.