I notice that any time I push a Change to a PR this triggers nearly all CI runs to run a full build of all the boards and ports,
even though nothing changes for those boards.

That is because most/all ports use these triggers :

on:
  push:
  pull_request:
    paths:
      - '.github/workflows/*.yml'
      - 'tools/**'
      - 'py/**'
      - 'extmod/**'

I think it would make sense to exclude the folder : using : '!tools/mpremote/**'

on:
  push:
  pull_request:
    paths:
      - '.github/workflows/*.yml'
      - 'tools/**'
      - '!tools/mpremote/**'
      - 'py/**'

There are 20 workflows that trigger on tools/**

Port Build Workflows (17 total)

I think these should exclude the tools/mpremote path:

1. .github/workflows/ports_alif.yml
2. .github/workflows/ports_cc3200.yml
3. .github/workflows/ports_esp32.yml
4. .github/workflows/ports_esp8266.yml
5. .github/workflows/ports_mimxrt.yml
6. .github/workflows/ports_nrf.yml
7. .github/workflows/ports_powerpc.yml
8. .github/workflows/ports_qemu.yml
9. .github/workflows/ports_renesas-ra.yml
10. .github/workflows/ports_rp2.yml
11. .github/workflows/ports_samd.yml
12. .github/workflows/ports_stm32.yml
13. .github/workflows/ports_unix.yml
14. .github/workflows/ports_webassembly.yml
15. .github/workflows/ports_windows.yml
16. .github/workflows/ports_zephyr.yml
17. .github/workflows/ports.yml

And there are two other workflows that I suggest to also exclude

18. .github/workflows/code_size.yml - checks code size metrics across multiple ports ( mpremote does not change firmware sizes)
    19 .github/workflows/biome.yml - javascript code quality checks ( perhaps limit to 'ports/webassembly/**' ?)

Workflows that SHOULD Trigger on mpremote ( keep unchanged)

• .github/workflows/mpremote.yml - builds and packages mpremote itself
• .github/workflows/mpy_format.yml - tests .mpy format and tools (includes tools/ testing)
• .github/workflows/code_formatting.yml - formatting verification
• .github/workflows/ruff.yml - Python linting
• .github/workflows/codespell.yml - spell checking
• .github/workflows/commit_formatting.yml - commit message validation

But as I do not have a full view of everything - i wanted to check if there may be a rationale or need that i do not see / understand.

Happy to create a PR for these

Why Change:
While I do not think the CI runs incur any charges, for this project - it does take actual time to run and holds up other runs that are more useful.

This can be clearly seen in last month's CI performance reporting :

• Avg job run time: 3m 59s
• Avg job queue time : 22m 1s

where the trend seems to be that that delay is climbing significantly.
There are additional interesting stats on runtime that may be relevant to optimize which actions run when.

Not to mention that there is actual energy used by these runs in some GH datacenter somewhere on this single planet of ours.