But what speed issues are you having ?
See
https://lafibre.info/remplacer-livebox/mise-en-route-leox-lxt-010h-d/msg974228/#msg974228.
He has a few percent of loss in upload, leading to a very slow TCP upload.
He has the same issue with LXT-010G-D and LXT-010H-D, and either with an OpenWRT router or with the Livebox 5 (Ethernet WAN port).
When using the Livebox 5 integrated ONT, everything works correctly.
He needs HW_HWVER to be set, so it's an ALCL OLT.
Here only @V3yz seems to be in the same configuration, and has no problem.
Other people who reported here on Orange didn't need HW_HWVER, so they are behind an HWTC OLT.
Most people replacing the ONT on Orange used Lantiq models, and I don't think anyone reported similar issues.