No it’s not. Per package info the latest version is framework-libopencm3-1.10000.200730 meaning LibOpenCM3 as of 2020 July 30th, which maps to the state at commit 24bef9c4. If you pull that commit and execute maketo generate the nvic.h header files, you will see that, e.g. with Meld as a comparison tool, it is exactly the same as the what PlatformIO packages currently.
Code that interfaces with libopencm3 must then also be compatible withthat version – or libopencm3 must be updated, as per above.
Indeed libopencm3 is not a PlatformIO project. It has no platformio.ini or anything and isn’t intended to be one. However, you can use it as a package source for framework-libopencm3.
Per above
Per package info the latest attainable version is toolchain-gccarmnoneeabi-windows_amd64-1.90301.200702 so that’s 9.3.1. Since you seem to be wanting gcc-arm-none-eabi-10-2020-q4-major-win32.exe from a local installation, you’ll need to point the package source to a local path. As documented here, the general file:// protocol works. Mind that for PlatformIO to recognize something as a valid package source, the root folder of the package will need to have package.json akin to what you see in C:\Users\<user>\.platformio\packages\toolchain-gccarmnoneeabi\package.json with update version information. (Equivalent if you want to change the libopencm3 source).