Migrating to new hardware - HBA and migration questions

Hello there ! I am about to migrate my current TrueNAS Core running on HP DL380 G9 to TrueNAS Scale on a custom tower PC due to physical office space and noise limitations.

New specs - Fractal Meshify 2 XL , AMD 5600X , ASRock X570D4U , 128GB Micron ECC RAM , Lenovo 530-16i (Broadcom AVAGO 9400-16i)

Question one: I want to transfer all my pools,users,groups,scrub and rsync schedules from the CORE to SCALE. Basically to safely migrate everything since I am CG artist and amateur in the IT area and I’m not sure how long it will take me to redo everything if I make a mistake. Following the documentation I have chosen to upgrade my 13.0-U6.4 to 24.10.1 Electric Eel though changing the update train. Then after installing 24.10.1 on the new machine I will be able to physically transfer the HDDs from the DL380 and finish the migration. Am I right here ? (I don’t have any pool encryptions enabled)

Question two: I was hesitating which HBA to buy. I wanted to buy a new unit just to be safer that it won’t burn soon but I didn’t had a lot of budget so I bought an Lenovo 530-16i from Ebay.
I read that people had errors with older firmware so I updated the firmware to 24.00.07.00 following this instruction lenovo_430-x_hba_firmware_BIOS_update.md · GitHub
Then I installed in on a test bench with a fresh SCALE installed and the HDDs were visible. Using dmesg | grep mpt I could see the correct HBA info and the hard drives that I installed through the HBA.

[ 3.526118] mpt3sas_cm0: SAS3416: FWVersion(24.00.07.00), ChipRevision(0x01)

I did flashed it with the latest Lenovo firmware because the latest BROADCOM was 24.00.00.00 from 2022 - Now I can’t use sas2flash or sas3flash, only storcli which is not installed in TrueNAS by default.
Is this a mistake and are there any benefits of cross-flashing the card to Braodcom ?

Question three: Can you recommend me a good 10G SFP+ PCIe card that is compatible with SCALE ?

I am sorry for the long post,but I really want to be safe with this double migration. Thanks in advance.

How many drives you have in the old system?

2 Boot SSDs and 8 WD Gold HDDs for now. Soon I will need to expand the HDDs. I run mirrored vdevs ,no RAIDZ.

Well, the easiest way - however not sure that it will work for a CORE-SCALE upgrade, is to put together the new machine, but first only with boot disk(s)
INstall a fresh TrueNAS.
Return to the old machine and save your config file to a pen drive.
Import the settings to the new machine. If it works, its OK, if not, you should make some screenshots from your needed settings and replicate then on the new machine.
When its done, you can move the data HDDs too into the new machine. (as I remember, you dont have to export them, the new system will recognise the pool and ofer the oprion to import them.) The pool(s) should appear in the available pools.
Use the GUI for importing the pools, using the CLi is not recommended.
You might need to upgrade the pools, to a newer version of ZFS. But wait with it, because, if you need to fall back to the original machine for any reasons, it might not be able to use the pool, that has been upgraded to a newer version of ZFS. (I learned it the hard way.)
Regarding question two:
I use an IBM 1015 card for my NAS reflashed to IT mode. I have it for years now, and I have absolutely no problems with it.
I use it with 4 and 6 TB HDDs.
Today they are available on eBay under around 50 EUR.
What you need to check is, if there is any HDD size limitations for the usable HDDs. ( I bought a real cheap, ASUS HBA, but that could not see bigger than 2TB Drives.)
Regarding question 3: I still did not install my 10G network, however already did some research.
YOu can buy used NIC on eBay from like 30EUR, or about for a 100 EUR a new one.
It might bepractical to buy a PCIe 4x card instead the 8x, because this MoBo have only 3 PCIe slots and only one of them is 16x, (and as I quickly read, there are also some limitations with the 16x/8x speed, depending, on how do you populate the other slots… As I understood, it has a 16x a 8x and a 1x slots available. (the 16x is limited to 8x, if the 8x is also populated)

Thank you a lot, Gyula. I will only need two slots - LAN and HBA , both of them use 8x lanes so the MB will do the job. For the LAN I will probably reuse the old one from my DL380. I will take into consideration your advice for the TrueNAS migration.

Best luck for the process!