There's a closed pull request on the void-packages repository

glibmm2.68: update to 2.76.0.
https://github.com/void-linux/void-packages/pull/43231

Description:
#### Testing the changes
- I tested the changes in this PR: **YES**

#### Local build testing
- I built this PR locally for my native architecture, glibc, x64

Note: Tested only telegram-desktop, unsure which applications depend on glibmm2.68