I successfully installed boot9strap on an old 3ds with 11.5 firmware on it with mt card used as ntrboot.
Mt card has wood firmare 1.62 and ace3dsplus hardware on it with spongbob icon, i followed this guide in the link
https://gbatemp.net/threads/ace3ds-plus-can-now-be-used-for-ntrboot.492072/#post-7757444
Successfully installed ntrboot on my mtcard then i followed 3ds all version method ntrboot guide from install boot9strap which includes magnet trick. After tried for couple of times i installed boot9strap on my 3ds.
3ds guide link
https://3ds.guide/installing-boot9strap-(ntrboot)
Mt card has wood firmare 1.62 and ace3dsplus hardware on it with spongbob icon, i followed this guide in the link
https://gbatemp.net/threads/ace3ds-plus-can-now-be-used-for-ntrboot.492072/#post-7757444
Successfully installed ntrboot on my mtcard then i followed 3ds all version method ntrboot guide from install boot9strap which includes magnet trick. After tried for couple of times i installed boot9strap on my 3ds.
3ds guide link
https://3ds.guide/installing-boot9strap-(ntrboot)