Thank you, @Alain for the information.
I plan to buy one of the upcoming Apple Silicon 16’ MacBook Pro, and I planned to make a server of my M1 mini. But it won’t run under Mojave.
If I end by subscribing to AS, I will follow your advice and use an Intel Mac as a server. I’ll do it only if I subscribe to AS, because I don’t have players that support Direct mode, except my old A+ 2.5.
Direct Mode still work with Catalina, but it stopped at 10.15.5 if i remember… Apple made more changes in audio extension and with the security update after i never get it back.
Exactly, I tried with Catalina, and it was a nightmare so I went back to Mojave, and I am a happy man !!
Thank you @RunHomeSlow for providing useful hacks.
I downloaded Mojave from Apple’s servers.
If I subscribe to AS, I may even install one server with an Intel Mac under Mojave for AS. And another server with the M1 mini for all the other players.
Not knowledge enough for that, i just rewrote the thing to made it clearly for beginners with Terminal… 
A+ 2.5 has an excellent sound in Direct mode under El Capitain. I enjoy listening to it. It’s a bit like playing vinyls.
@Doudou
For me with my audio environment, Direct Mode make a real difference and all the interest of Audirvana 3.5 or AS. I would not have suscribed to AS without.
If your El Capitan machine supports MoJave you can already test AS with Direct Mode !
My El Capitain computer is a 2008 Intel Duo Core MacBook Pro. El Capitain is the last OS to which this computer can be upgraded. Until I buy a new Apple Silicon Macbook Pro, I can’t downgrade my i7 MacBook Pro to Mojave. I need it under Big Sur, because it serves me for my work.
I used Direct mode for years, and I didn’t understand why it stopped working. And I ended by forgeting about it. Thank you for explaining me and remininding me about it. It gave me the idea to restart using this old MacBook Pro that was only serving as a printer server.
excellent !
Well I’ve decided to ditch Roon when the sub expires. Which will be June next year. I haven’t used in it in weeks. On hindsight, would have been better to sub for a month or two. Oh well…
AS gets used here on a daily basis and happily plays on both my Office Windows laptop and my MacBook Air in the living room. It still seems to have some issues playing radio stations, but otherwise it works fine.
I’m playing local music and streaming from both Qobuz and Tidal. I also stream Apple Music. So plenty of music to go around with. Apple Music mostly on my phone when I’m driving my forklift at work. They have really great personal recommendations and playlists.
Another plus for me is the subscription cost. AS x2 is only slightly more expensive compared to a single Roon subscription when you look at it annually.
I also have jRiver running on my Windows laptop. It has excellent tagging options. And I’m using it to tag my whole library. Both music and video. I’m using it to watch video files. It has a really nice theater mode.
Edit:
I’ve discovered something else as well. Recently I’ve bought a pair of Presonus Eris E4.5 BT speakers. And connect my Mac to them through Bluetooth.
My Mac plays sound through them no problem. Apple Music works fine. So does AS. But Roon does not. Roon doesn’t recognize the speakers, while AS picks them up no problem.
I’ve discovered that Roon seems to have a lot of issues recognizing Bluetooth systems. Even when the host OS fully supports them.
Hi, @Doudou & many thanks for the advice.
I added music file one after another, some of them big files, some of them up to 100GB in size because many of my files are Discographies, should that be a problem?
This is truly a great Forum where you feel welcome, not least because of you & a few others, Thanks again. 
Hi @Tippe , you’re welcomed.
I’m not sure to have understood what you meant by saying that some files have 100GB in size.
You should know that on Windows, AS has a bug that prevent it from managing files that are greater than 2 GB in size. These filesjust won’t appear in the player.
An advantage of Audirvana over Roon is that it has a nice forum with friendly users.
Friendly users who help each other, and are not paid for the work they do instead of Audirvana’s support. 
Hi,@Doudou, what I mean is that some folders can contain up to 2000 audio files.
This is OK. Anyway, if you have any files that are greater than 2 GB (it can happen with some DSD 256 files), don’t be surprised if they will not appear in AS.
Imagine if we all had to do this? It’s safe to say that nobody would be using Audirvana.
You first assume it will work without problems, and only if you have problems employ these time consuming procedures.
He runs the analysis for more than a month, and it’s not progressing.
Dear Doudou, maybe it can happen. But I just played these days 2 SACD ISO bigger than 2 GB (Nat King Cole, DSD64).