The other thread is about NFSv4. vers=3 is still the default for kernel mounts.
and then did mount -o remount,rw /storage, which worked fine
Boot code in initramfs is using busybox mount while LE user mode is having util-linux mount + nfs-utils mount.nfs. There may be differences in behavior, but the tools are identical in the bisected versions.
Remain the kernel changes. For NFS (only) they are;
Code
> git --no-pager log --oneline v6.6.63...v6.6.66 -- fs/*nfs*
37dfc81266d3 nfsd: fix nfs4_openowner leak when concurrent nfsd4_open occur
1cecfdbc6bfc nfsd: make sure exp active before svc_export_show
065902117a5b nfs: ignore SB_RDONLY when mounting nfs
229a30ed42bb NFSv4.0: Fix a use-after-free problem in the asynchronous open()
dde654cad08f NFSD: Prevent a potential integer overflow
1dfc79bfc544 NFSD: Fix nfsd4_shutdown_copy()
bd8524148dd8 nfsd: release svc_expkey/svc_export with rcu_work
028417543535 NFSD: Cap the number of bytes copied by nfs4_reset_recoverydir()
eb51733ae5fc NFSD: Prevent NULL dereference in nfsd4_process_cb_update()
But I do see nothing obvious.