I also created a list on mdl with this info and more, it is here.

• The Lost Tomb:  the start of Wu Xie's tomb raiding adventures 
• The Lost Tomb 2: Wu Xie starts a new adventure in an undersea tomb
• The Lost Tomb 2: Explore with the Note: Wu Xie continues his adventure on Changbai Mountains.
• Ultimate Note: A continuation of the Lost Tomb series.
• Adventure Behind the Bronze Door: Wu Xie explores Zhang Qiling's past.
• Tomb of the Sea: After all these years, Wu Xie is hardened by the grave-robbing life and is different from his innocent self in The Lost Tomb.
• Reunion: Sound of the Providence: Wu Xie has finally retired from grave robbing until he gets a text message from his missing uncle entangling him in another mystery.
• Reunion: Sound of the Providence 2: Second season of Reunion.
• Mystic Nine [optional]: this is a stand-alone prequel set during the 1930s. It does not include Wu Xie, Qiling, or Pangzi but involves the nine major grave robbing families (including Wu Xie's) in Changsha. It helps to watch this because it involves the family politics that is mentioned throughout the rest of the shows. 

If you want more information, there is a fandom wiki of the books the shows are based on here and the show wiki here (both contain spoilers!).

If you have any more questions, feel free to ask~

What about the Mystic Nine movie? 

Okay Cool Thanks @taomubiji I’m looking forward to it.

Thank you so much! I was gonna watch The Lost Tomb, but then I saw the various other works that are in the series and I was confused about what order these dramas should be watched in. Thank you!

I've only watched the latest Reunion the sound of providence and now the Ultimate Note and I'm loving the Ultimate Note very much ,, the story is so good and the acting is excellent also the Bromance is  heightened 

I have watched The lost tomb 1 and 2 now. Can I watch Ultimate Note now or should I wait and watch "The Lost Tomb 2: Heavenly Palace on the Clouds" (that hasent been realesed yet) first?  If that is so, do anyone know when it will air? 

Ok, thank you! So there wont be any spoliers or things i dont understand if I watch Ultimate note before The lost tomb 2: HPOTC then? 

 LunaAdr:

Ok, thank you! So there wont be any spoliers or things i dont understand if I watch Ultimate note before The lost tomb 2: HPOTC then? 

You will be a little confused about some things in the first episode because they talk about something included in The Lost Tomb 2:HPC. I don't think it's such a big spoiler that it's worth waiting for that show to air, especially because the air date is still not confirmed. But it will probably air in the first half of 2021. What happens in LT2:HPC is not that important plot-wise for Ultimate Note.