Wireshark 2.6 doesn't find the interfaces and exits the program.

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Can you paste the contents of the Help | About Wireshark | Wireshark dialog box?

In fact, I can't. Wireshark closes itself after less than 5 seconds. Can I add somewhere a screenshot?

Maybe use tshark from a command prompt then:

"path\to\tshark.exe" -v

Where path\to is the appropriate path to your install of Wireshark, likely to be "C:\Program Files\Wireshark", or "C:\Program Files (x86)\Wireshark", and if it includes spaces will have to be quoted as in the example.

OK, that shows that npcap has been found and is being used. Something is up with the interfaces on your machine that prevents the initial scan of interfaces succeeding.

Can you open a PowerShell prompt and show the output of Get-NetAdaptor?

output:

PS C:\Users\Tom> Get-NetAdapter

Name                      InterfaceDescription                    ifIndex Status       MacAddress             LinkSpeed
----                      --------------------                    ------- ------       ----------             ---------
Wi-Fi                     Intel(R) Dual Band Wireless-AC 7265          23 Up           10-02-B5-2E-74-80     173.3 Mbps
VirtualBox Host-Only N... VirtualBox Host-Only Ethernet Adapter        19 Up           0A-00-27-00-00-13         1 Gbps
Mobiel 2                  Dell Wireless 5809e Gobi™ 4G LTE Mob...      13 Disconnected 90-93-80-52-53-4A          0 bps
Ethernet                  Intel(R) Ethernet Connection (3) I21...      12 Disconnected F8-CA-B8-45-5B-92          0 bps
Npcap Loopback Adapter    Npcap Loopback Adapter                        6 Up           02-00-4C-4F-4F-50       1.2 Gbps
Bluetooth-netwerkverbi... Bluetooth Device (Personal Area Netw...       5 Disconnected 10-02-B5-2E-74-84         3 Mbps

FYI

C:\Program Files\Wireshark>tshark.exe -D
1. \Device\NPF_{4F85C07A-63A5-4AE5-87FF-6D4E929FD5AE} (LAN-verbinding* 11)
2. \Device\NPF_{9D7312CD-AE4C-48B8-9436-3B8558F477CF} (LAN-verbinding* 5)
3. \Device\NPF_{3A0BCE39-91E2-4111-A179-3E573E66370C} (Bluetooth-netwerkverbinding)
4. \Device\NPF_{FBD7D021-B7D1-4F9B-9064-851B283605DD} (Wi-Fi)
5. \Device\NPF_{CD853BB4-2C17-4076-BB16-D044F823E9DF} (VirtualBox Host-Only Network)
6. \Device\NPF_{54999DCB-50FD-4058-BF37-EAC4CF949DF1} (Ethernet)
7. \Device\NPF_{6A5F1E01-9696-47F0-868E-58768B6A0A11} (Mobiel 2)
8. \Device\NPF_{53ADB2E7-0520-4438-A388-E4A69E5A5B46} (LAN-verbinding* 10)
9. \Device\NPF_{3D15719B-51D4-4D60-B0B1-DDC021D5BA48} (Npcap Loopback Adapter)
10. \Device\NPF_{401DE622-CB5E-46C5-999E-AFC2CF06C767} (LAN-verbinding* 2)
11. \Device\NPF_{C430DB3A-3DEB-47C5-9F9F-DF10D4EB9825} (LAN-verbinding* 12)

Strange, no?

The one that is (somewhat) out of the ordinary is:

Mobiel 2  Dell Wireless 5809e Gobi™ 4G LTE Mob...   13 Disconnected 90-93-80-52-53-4A 0 bps

Is there any way you can remove or "delete" that so Windows can't see it?

tshark just lists the interfaces configured, Wireshark actually tries to open them to discover more info, such as the link type and this is where bad things are happening.

I disabled Mobiel2. Unfortunately same result!

How did you disable it? Does it still show up in the tshark -D output?

I disabled Mobiel 2 via Device Manager.

C:\Program Files\Wireshark>tshark.exe -D
1. \Device\NPF_{4F85C07A-63A5-4AE5-87FF-6D4E929FD5AE} (LAN-verbinding* 11)
2. \Device\NPF_{9D7312CD-AE4C-48B8-9436-3B8558F477CF} (LAN-verbinding* 5)
3. \Device\NPF_{3A0BCE39-91E2-4111-A179-3E573E66370C} (Bluetooth-netwerkverbinding)
4. \Device\NPF_{FBD7D021-B7D1-4F9B-9064-851B283605DD} (Wi-Fi)
5. \Device\NPF_{CD853BB4-2C17-4076-BB16-D044F823E9DF} (VirtualBox Host-Only Network)
6. \Device\NPF_{54999DCB-50FD-4058-BF37-EAC4CF949DF1} (Ethernet)
7. \Device\NPF_{53ADB2E7-0520-4438-A388-E4A69E5A5B46} (LAN-verbinding* 10)
8. \Device\NPF_{3D15719B-51D4-4D60-B0B1-DDC021D5BA48} (Npcap Loopback Adapter)
9. \Device\NPF_{401DE622-CB5E-46C5-999E-AFC2CF06C767} (LAN-verbinding* 2)
10. \Device\NPF_{C430DB3A-3DEB-47C5-9F9F-DF10D4EB9825} (LAN-verbinding* 12)

OK, so that guess didn't seem to work out, although it's possible npcap might have need some sort of reset to really drop the Mobiel NIC out of the system.

Only thing I can suggest is to try to get tshark to open each interface in turn, maybe use the -L parameter to list the link types, e.g.

tshark -L -i 1

repeating for each IF and see if one has issues.