How to fix vsftpd error: 500 OOPS: cannot change directory

I am trying to setup vsftpd for anonymous-only, read-only access on my Ubuntu 20.04 VM. Home directory is /home/ftp/filebase. When I try to login, I get the error

500 OOPS: cannot change directory: "/home/ftp/filebase"

and am kicked out.

There are a few questions on this here already. Most suggest to disable SELinux (not installed here) or to adjust directory permissions to give access up to the top:

# ls -al
total 2097232
drwxr-xr-x   4 root root       4096 Jul 24 18:32 home
/home# ls -al
drwxr-xr-x  3 ftp   ftp   4096 Jul 24 18:34 ftp
/home/ftp# ls -al
drwxr-xr-x   3 ftp  ftp  4096 Jul 24 18:34 .
drwxr-xr-x   4 root root 4096 Jul 24 18:32 ..
drwxrwxr-x 198 ftp  ftp   212 Mai 17  2018 filebase

So all directories up the line have read and execute permissions for everyone.

my config:

listen=YES
listen_ipv6=NO
anonymous_enable=YES
local_enable=NO
anon_root="/home/ftp/filebase/"
no_anon_password=YES
hide_ids=YES
dirmessage_enable=YES
use_localtime=YES
xferlog_enable=YES
connect_from_port_20=NO
pasv_enable=Yes
pasv_min_port=40110
pasv_max_port=40210
ls_recurse_enable=YES
secure_chroot_dir=/var/run/vsftpd/empty

The logfile is pretty silent:

Fri Jul 24 19:16:59 2020 [pid 7822] CONNECT: Client "192.168.1.2"
Fri Jul 24 19:16:59 2020 [pid 7818] [ftp] OK LOGIN: Client "192.168.1.2", anon password "<no_password>"

Please, what am I missing?

anon_root=/home/ftp/filebase/

500 OOPS: vsftpd refusing to run with writable root inside chroot()