If you should decide to go inhouse, I can warmly recommend checking the *frappe framework*, with which the open-source ERPNext was built. Compared to other such things this is truly open source (not like odoo and others, which really try to catch you in with being "open-source" and then let you pay up for the features you really need).

It is very powerful and comes with so many batteries included and is actually quite fun to develop with.

https://frappeframework.com/

Here is a story of a big financial institution betting on inhouse dev using frappe. (There is a TLDR on the bottom of that page ;) )

https://zerodha.tech/blog/being-future-ready-with-common-sen...

All the best <3