Sergey Poznyakoff is based in Odessa, and maintainer of a couple of high profile GNU projects: https://gray.gnu.org.ua/project/list/ (tar, cpio, pax, mailutils, radius, gdbm, ...)
he is still committing on GitHub during the war, so looks good for now.
then there are Blynk and PlatformIO based in the Ukraine (Kiev), essential for embedded. Grammarly has not that much open sourced, but they are huge.