I can confirm the issue (Arch). The system is fully up-to-date.
$ haxelib install hmm
Error: Failed with error: load.c(237) : Failed to load library : /usr/lib/neko/ssl.ndll (/usr/lib/neko/ssl.ndll: undefined symbol: mbedtls_ssl_get_verify_result)
$ yay -Q | grep -E 'neko|haxe|mbedtls'
haxe 4.3.7-6
mbedtls 4.2.0-1
mbedtls3 3.6.7-1
neko 2.4.1-6
Installing the latest git version produces the same result:
$ haxelib git hmm https://github.com/andywhite37/hmm.git
Installing hmm from https://github.com/andywhite37/hmm.git
Cloning Git from https://github.com/andywhite37/hmm.git
Syncing submodules for Git
Downloading/updating submodules for Git
Current version is now git
Done
Error: Failed installing dependencies for hmm:
Failed with error: load.c(237) : Failed to load library : /usr/lib/neko/ssl.ndll (/usr/lib/neko/ssl.ndll: undefined symbol: mbedtls_ssl_get_verify_result)