Can't upgrade due to low disk space on /boot (22.04 to 24.04)

sudo do-release-upgrade fails with:

Not enough free disk space The upgrade has aborted. The upgrade needs a total of 621 M free space on disk '/boot'. Please free at least an additional 152 M of disk space on '/boot'. You can remove old kernels using 'sudo apt autoremove' and you could also set COMPRESS=xz in /etc/initramfs-tools/initramfs.conf to reduce the size of your initramfs. Restoring original system stateAborting

now my problem is that my /boot partition (installed and sized and formatted by kubuntu 22.04 installer) is only 704MB:

/dev/nvme0n1p2              704M  205M  448M  32% /boot

and my only installed kernel takes about 200MB:

$ ls -lah /boottotal 197Mdrwxr-xr-x  5 root root 4.0K aug   30 16:41 .drwxr-xr-x 22 root root 4.0K juuni 16  2022 ..-rw-r--r--  1 root root 281K juuli 30 17:33 config-6.8.0-40-genericdrwx------  4 root root 4.0K jaan   1  1970 efidrwxr-xr-x  5 root root 4.0K aug   30 16:38 grublrwxrwxrwx  1 root root   27 aug   30 13:38 initrd.img -> initrd.img-6.8.0-40-generic-rw-r--r--  1 root root 173M aug   30 13:38 initrd.img-6.8.0-40-genericlrwxrwxrwx  1 root root   27 aug   30 16:38 initrd.img.old -> initrd.img-6.8.0-40-genericdrwx------  2 root root  16K märts  2  2021 lost+found-rw-r--r--  1 root root 179K veebr  6  2022 memtest86+.bin-rw-r--r--  1 root root 181K veebr  6  2022 memtest86+.elf-rw-r--r--  1 root root 181K veebr  6  2022 memtest86+_multiboot.bin-rw-------  1 root root 8.3M juuli 30 17:33 System.map-6.8.0-40-genericlrwxrwxrwx  1 root root   24 aug   30 13:38 vmlinuz -> vmlinuz-6.8.0-40-generic-rw-------  1 root root  15M juuli 30 18:17 vmlinuz-6.8.0-40-genericlrwxrwxrwx  1 root root   24 aug   30 16:38 vmlinuz.old -> vmlinuz-6.8.0-40-generic

So there is nothing anymore I can remove from there... and it still wants me to free up additional 152MB?

1. Is there anything I can do to increase the /boot size somehow?

nvme0n1                259:5    0 238.5G  0 disk  ├─nvme0n1p1            259:6    0   512M  0 part  /boot/efi├─nvme0n1p2            259:7    0   732M  0 part  /boot└─nvme0n1p3            259:8    0 237.3G  0 part  └─nvme0n1p3_crypt    252:0    0 237.2G  0 crypt ├─vgkubuntu-root   252:1    0 236.3G  0 lvm   /└─vgkubuntu-swap_1 252:2    0   976M  0 lvm   [SWAP]

I don't know... maybe nuke the vgkubuntu-swap_1 somehow and add the freed space from nvme0n1p3 to nvme0n1p2? But I really don't know how.

2. Or is there anything I can do to reduce the 621MB do-release-upgrade asks for somehow?

3. Or is there some easy way to move /boot partition somewhere else (temporarily) if I were to add another disk or USB stick to system? Do the upgrade and move "boot" back (if it doesn't actually require this absurd amount of space after install)?