I manage 1000s of Windows servers from my Linux laptop and desktop. I also manage 1000s of Linux boxes too.

I don't denigrate your approach with Windows but please don't tell me I can't do x because I literally can on Linux.

My Linux devices are often domain joined - I log into an AD (used to be eDirectory but wth) I don't care. AD is quite a decent LDAP directory - not as good as eDir though but I doubt many here are capable of discussing that little number. I make huge use of Kerberos - all my browsers can connect to my Apaches etc with SSO if I so wish. Let's Encrypt and putting AD and vCentre CA certs into the various places like /usr/local/share/whatever and running the maint script keeps the browsers from getting upset.

I used to have email via GroupWise but we moved to Exchange back in the day (2011 from memory) I've used Evolution EWS since then. Provided you get your endpoints and DNS in line then you can use Kerberos, otherwise it's NTLM ... lol. You can put Exchange behind HA Proxy. That gets you loads of extra goodies like being able to hide squidgy bits and upping the SSL/TLS to the point where you can make say Exchange 2013 PCI/DSS compliant.

I have no idea why you fixate on GIMP, there are so many graphics apps available it is quite embarrassing. Have a look at say Krita.

Ditch OpenOffice. LibreOffice is capable and where the development is happening. Back in the day I was a MS Office trainer (and a few other things). I know what leading and kerning actually means and dealing with hanging indents, n and m dashes and all the rest. Upper case used to be stored in the upper row of cases in a printer's workshop, leading was shims of lead to move letters up and down. I taught Lotus 1-2-3 macros to company execs as well as Super Calc and even Excel. I can write macros in more languages badly than I care to recall. I wrote a Finite Capacity Scheduler (yes: finite) in Excel VBA for a pie factory near Plymouth. I'm quite happy with LO. It's quite capable in my opinion.

I've got loads of CAD options - I'm a fan of 3D printing. LibreCAD and OpenSCAD are absolutely belting and getting better every month. Blender is quite capable I'm told. I have not even started on that little number but I gather it is absolutely the dog's nadgers. Apparently film studios use it.

I have so many high quality options available to me using Linux. I'm 50 years old. I've used computers from ZX80 and I still have a Commodore 64 (with a USB interface now). My first real PC was a 8086. I managed to get a cracked copy of AutoCAD to work on my 80286 with a 80287 co-processor that my parents bought me for my birthday at something like £120 back in 1987ish.

I'm a sysadmin so not too fussed about IDEs but there are an absolute shitload of them available. Bear in mind the real difference between a Linux distro and Windows and Apples: We've always had an appstore and it is part of the system and not a bolt on.

When I type:

# emerge -Uve --deep --newuse @world
# yay -Syu
# apt update && apt upgrade

etc, I update everything. Everything. Apart from the first one (which may involve a pact with the old gods) they will all finish within a few minutes at most.

I've seen Windows updates last for days at worst. At best it takes at least 15 minutes. On average you'll need around 30 mins except for Defender updates.

So:

1) Take your pick - for me KDE
2) LO for Office apps. There are so many first class apps it's hard to create a starting point
3) Evo + EWS. OK I'll accept that there is only one app here. You do get all functionality including calendar. You also have more options for notifications
4) Really?
5) You have access to a ridiculous amount of software from a central source

I think that open source has already surpassed closed source stuff by quite a long way. I own my own company and live and die by my choices. I've been doing IT for about 30 years and for about the last 15 of those I have not used MS software on my personal gear.

I wrote this a while back but I do keep it up to date: https://www.mediawiki.org/wiki/Intranet - might be handy for someone integrating Linux in a Windows world.