I moved this to Desktop Environments, Budgie.
The answer is no. All Desktop Environments on EndeavourOS come “vanilla”, that is, without any custom themes or modifications. The only exception is the off-line install of Xfce, which is customised.
That means that if you want to add a custom sound at login, you need to do it yourself, EndeavourOS does not ship it (unless it is the default in the Desktop Environment).
I have no idea how this is done on Budgie, but I’m sure you can look it up yourself, or someone with more Budgie experience than me can tell you how to do it.