Hello I'm facing the exact same issues on macbook air m1 on latest macos. I've tried every solution/tweak for both client and server that I could google up.
Here is a gif showing me trying to delete a few files:
https://preview.redd.it/o3m0lio5n5171.gif?format=mp4&s=1ee06640ce047ba2c0c5b3ed451f4f953228b5b8
I've installed wireshark on macos, and while i'm not an SMB protocol pro and know nothing about it but a single file copy from laptop to server is around 3200 smb protocol messages and that doesn't look right to me at all.
On unraid side in the /var/log/samba/log.smbd log I see hundreds of these messages per second when I browse a directory:
[2021/05/24 23:05:10.725925, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.727676, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.731051, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.731652, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.733008, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.733479, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.735057, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.735696, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.737710, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
ad_open_rsrc: SMB_VFS_CREATE_FILE failed
[2021/05/24 23:05:10.738508, 0] ../../source3/lib/adouble.c:2102(ad_open_rsrc)
I know this is a problem with macos smb implementation, but it would be really nice to have a solution. I have a friend with synology and he doesn't have any of such issues at all. All other my windows and linux devices work just fine and very fast.