You can compile just fine Firebird 4/5 on Oracle Linux 8 Ampere V1 (arm64) all you need is GCC Toolset 12 enabled as described here .
Also same steps work for Oracle Linux 8.x on x86-64.
sudo dnf group install "Development Tools" sudo dnf install libicu-devel cmake git sudo dnf install gcc-toolset-12 scl enable gcc-toolset-12 bash git clone https://github.com/FirebirdSQL/firebird.git cd firebird ./configure --with-builtin-tommath --with-builtin-tomcrypt make
