Mint 20 problem, looks like not the right kernel

I followed the details in the first post and ended up with errors starting LinuxCNC. Stepconf worked fine, Latency Test worked but indicated horrible latency.
The Update Manager reports that I'm on kernel 5.4.0-26. I'm pretty sure that disagrees with what is on the first page:wget ftp.us.debian.org/debian/pool/main/l/lin..._4.9.228-1_amd64.deb

So something went wrong. Do I just need to get the correct kernel?

Thanks,
Steve

-Power on PC,
-hold down the "shift" key
-at the GRUB menu choose the 4.9 RT kernel
-press enter

Thank you tommylight. I should have figured that out...but didn't.
Latency is now where it should be (from previous on this computer).

I have both a motherboard parallel port and a PCIE parallel port (SUN1989). I'm pretty sure I looked for the card when I had the previous kernel and found it. Now, it has vanished from /dev. Any clues?

cat /proc/ioports |grep parport

dmesg |grep parp I get

lsmod | grep parp

sudo lspci -v | grep parp

sudo cat /proc/ioports | grep parport
[sudo] password for steve:
0378-037a : parport0
037b-037f : parport0

sudo dmesg | grep parp
[ 4.483609] parport_pc 00:02: reported by Plug and Play ACPI
[ 4.483687] parport0: PC-style at 0x378 (0x778), irq 7 [PCSPP,TRISTATE,EPP]
[ 4.582937] lp0: using parport0 (interrupt-driven).

lsmod | grep parp
parport_pc 28672 1
parport 49152 3 lp,parport_pc,ppdev

sudo dmesg | grep parp
[ 4.483609] parport_pc 00:02: reported by Plug and Play ACPI
[ 4.483687] parport0: PC-style at 0x378 (0x778), irq 7 [PCSPP,TRISTATE,EPP]
[ 4.582937] lp0: using parport0 (interrupt-driven).

I left off the lspci. My PCIE card is a Sunix with the SUN1989 chip. It has a serial port and a parallel port. lspci finds the serial port:
05:00.0 Communication controller [0708]: SUNIX Co., Ltd. Multiport serial controller
Subsystem: SUNIX Co., Ltd. Multiport serial controller
Flags: medium devsel, IRQ 11
I/O ports at cce0
I/O ports at ccc0
I/O ports at ccc8
I/O ports at ccd0
Capabilities: [40] Power Management version 3

but no mention of the parallel port on the card.

I thought I posted this, but it doesn't seem to exist.
I booted with the not real time kernel, finds the PCIE parallel port with no problem.

I don't understand what I'm getting from lspci -v | grep parp:
sudo lspci -v | grep parp
lspci: Unable to load libkmod resources: error -12

When I look for the serial port:
sudo lspci -v | grep ser
lspci: Unable to load libkmod resources: error -12
05:00.0 Communication controller [0708]: SUNIX Co., Ltd. Multiport serial controller
Subsystem: SUNIX Co., Ltd. Multiport serial controller

I can grep something else, like "lspci -v | grep Xeon" and it works fine. Putting "parp" in quotes doesn't help. "lspci -v" also works fine.

Looking at lspci -vvv:

First, the *not* real time kernel:
04:00.0 Communication controller [0708]: SUNIX Co., Ltd. Multiport serial controller
        Subsystem: SUNIX Co., Ltd. Multiport serial controller
        Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Interrupt: pin A routed to IRQ 32
        Region 0: I/O ports at cce0
        Region 1: I/O ports at ccc0
        Region 2: I/O ports at ccc8
        Region 3: I/O ports at ccd0
        Capabilities: [40] Power Management version 3
                Flags: PMEClk+ DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot+,D3cold-)
                Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
        Kernel driver in use: parport_serial
        Kernel modules: parport_serial

Now the same output from the real time kernel:
04:00.0 Communication controller [0708]: SUNIX Co., Ltd. Multiport serial controller
        Subsystem: SUNIX Co., Ltd. Multiport serial controller
        Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Interrupt: pin A routed to IRQ 11
        Region 0: I/O ports at cce0
        Region 1: I/O ports at ccc0
        Region 2: I/O ports at ccc8
        Region 3: I/O ports at ccd0
        Capabilities: [40] Power Management version 3
                Flags: PMEClk+ DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot+,D3cold-)
                Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-

It looks like they are identical until the last two lines. Is the driver not loading? I'm out of my depth on this.

LinuxCNC has its own driver. If you get the correct address then it should just work even if the Linux system isn't finding it.

parport_pc is handy for finding the port by index number (0, 1, 2...) but isn't needed to find it by address.