You can't use LFP batteries as a direct replacement in your UPS, no. The voltages and charge characteristics are different. What you can do is replace the UPS with a portable battery solution, like another poster suggested. I believe the Anker units are one of the few that can function as a UPS. Most sorta-can, but the key difference most of them lack is that they don't turn on automatically after fully discharging when the mains power comes back on. It's up to you if you need this particular feature.

Will Prowse on youtube I think has some videos comparing and contrasting the different units for this purpose.