By NVME adapter do you mean something like this? If so, will keep it in mind for a potential upgrade in future, it's not something that I can immediately get into for now.
Yea you put 2028r lol not 1028r On the site it says it has 2 hybrid slots. Are you using both of those? If not use that. Or just use https://www.amazon.com/SilverStone-Technology-Advanced-Solution-ECM22/dp/B075ZNWS9Y/ref=sr_1_10?dchild=1&keywords=nvme+pcie+adapter&qid=1618945284&sr=8-10
that device will give you 2 more nvme slots. You could put 2 in together and put them in raid 1 so you have some fault tolerance.
No you can get something like this https://www.amazon.com/SilverStone-Technology-Advanced-Solution-ECM22/dp/B075ZNWS9Y
These above are just some examples which are nvme expansion but provide sata port. Some are even describing that sata will connect.
Here are links to the things I've purchased from Amazon and eBay for my 4,1 Mac Pro that I flashed to 5,1 (in reverse order):
Samsung 970 EVO Plus SSD 250GB - M.2 NVMe Interface Internal Solid State Drive with V-NAND Technology (MZ-V7S250B/AM)
Shaluoman Mini PCI-E Adapter for BCM94360CD/BCM94331CD
Broadcom BCM94360CD 802.11ac 1.7Gbps WiFi card BT (to add handoff capabilities with MacOS Mojave)
Apple Mac Pro 2009 3.46GHz 6-Core CPU Tray w/ FW Upgrade & Buyback
MaxPower eSATA 6G Pro PCIe Controller Card
<strong>Samsung</strong> 850 PRO - 256GB - 2.5-Inch SATA III Internal SSD (MZ-7KE256BW)
The first thing you should do is add an SSD or NVMe drive. It will make your Mac Pro seem like as fast as any modern PC.
This little guy should work. One slot for nvme and one for sata https://www.amazon.com/SilverStone-Technology-Advanced-Solution-ECM22/dp/B075ZNWS9Y
It supports SSD's yes. It does NOT support booting from NVMe (PCIe) M.2's (but you can still use them as a secondary/storage drive with an add in card, I've done that before using one of these https://www.amazon.com/dp/B075ZNWS9Y/ref=twister_B076MW8LPS?_encoding=UTF8&psc=1). But the "regular" 2.5" SSD's work just fine in the front bays. IIRC it only supports SATA II (6.0Gbps) speeds though. I'd strongly recommend getting 2.5" trays for it though. They aren't strictly needed for operation, but keeps stress off your components and keeps them properly seated.
The other one I mentioned is pricier, it's a Cisco UCS C240 M3 but it's an all around much better server (more bays, better processors, more efficient, better expansion options, much better server management console, even looks cooler love my C240.) Drive trays for this tends to cost more than the dells.