Last week I performed a firmware upgrade to v1.0.01.07 which was released on 2022-01-28. This solved the problem for me.

Here is a dedicated version for the RV26X family:https://www.cisco.com/c/dam/en/us/td/docs/routers/csbr/RV260/USB_Compatibilty_Matrix/RV26X_compatibility_matrix.pdfUnfortunately it says:"Cisco will no longer support USB modems/dongles for RV260/260P/...

Same issue here. I bought and configured this router previous week. After updating the router with the latest firmware I noticed that my WAN port was set to 10Mbps and was unable to connect to my ISP. After downgrading it to v1.0.00.13 I was able. @c...