Steam reports incorrect free space

Your system information

Steam client version: Jun 7 2022
Distribution Arch Linux in borealis VM on Chromebook
Opted into Steam client beta?: [No]
Have you checked for system updates?: [Yes]

Please describe your issue in as much detail as possible:

The default drive is mounted as brtfs and I've added an external drive image of 800GB which is formatted with brtfs as well. When I check the disk space the available free space is reported as a random number, for the external drive I've seen 16.777.216 TB free of 799 GB, but also 40 GB games, 758 GB other, 3.57 GB free, the internal drive also gives the same number for free space, i.e. I've seen 16.777.216 TB and 3.57 GB. When I run df -h the free space reported is looks reasonable, i.e. disk size minus the size of the installed games.

When running steam with DBG_STAT=1 I get

statvfs64: ret 0 errno 11
  f_bsize : 4096
  f_frsize: 4096
  f_blocks: 209715200
  f_bfree : 198116978
  f_bavail: 197645154
statvfs64: ret 0 errno 11
  f_bsize : 4096
  f_frsize: 4096
  f_blocks: 3197592
  f_bfree : 1279520
  f_bavail: 773968
statvfs64: ret 0 errno 11
  f_bsize : 4096
  f_frsize: 4096
  f_blocks: 209715200
  f_bfree : 198116978
  f_bavail: 197645154

and multiplying block size and f_bavail seem to give the same number for free space like reported by the OS.

When I get 16.777.216 TB I can install games, so I started to install some games, but after initiating three downloads, the reported size for free went down to around 2GB again, and the additional disk space was reported as "Other". I've also tried to clean the download cache, but in the end it seems that the reported value for free space is kind of random. In all cases the values reported by statvfs64 seemed reasonable.

Steps for reproducing this issue:

Run steam in borealis on a chromebook
Go into Settings/Downloads/LibraryFolders and look at the available disk space

ValveSoftware / steam-for-linux