jks

So your Kiwi is not currently configured for the proxy service it seems. But after some checking I found I could connect to it at its current public ip address (on port 8073). On the admin page connect tab you have the menu entry set to "public ip" instead of "reverse proxy". Change it back, restart, and I'll bet you'll be fine.

Please don't do this. But there is a much better way using that 6.3 VAC transformer. In fact, it's perfect.

Use a modern low-dropout linear regulator chip (LDO) to get exactly 5V. E.g. a modern LTC / Analog Devices LT1085-5 in a friendly 3-pin TO-220 package can handle 3A output. It's $2-3 USD. It will need to attach to a small heatsink. There are complete schematics in the data sheet and on the web.
https://www.analog.com/media/en/technical-documentation/data-sheets/1083ffe.pdf

Just because you have a 6.3VAC transformer doesn't mean you'd get 6.3 VDC. If you use a full-bridge rectifier you'd get 6.3*sqrt(2) = 6.3*1.4 = 8.9 VDC. But this is fine for the LDO input which always needs to be higher than the output anyway. Yes, the 8.9 to 5V difference will be burned away as heat by the regulation (and you'll need a good heatsink for the LDO to handle that). You don't need an output inductor with an LDO. Just the recommended input and output capacitors to the chip (see data sheet).

You would essentially be building one of those ~$60 Ebay power supplies we recommend on our webpage. They use the same design.

From the CHANGE_LOG file:

v1.394  May 31, 2020
    Noise blankers and filters:
        Added the spectral noise reduction filter by Frank, DD4WH and Michael, DL2FW, via the
        Teensy-ConvolutionSDR and UHSDR projects. See: github.com/df8oe/UHSDR/wiki/Noise-reduction
        This noise filter works really, really well. Especially for voice signals.
        A good alternative to the LMS filters.

    Note that the Wild blanker and all the noise filters (wdsp, LMS, spectral) don't currently work
    with the modes: IQ, SAS and DRM (i.e. the 2-channel IQ modes). This will be fixed at some point.

This filter is on the main control panel, audio tab, "noise > filter" menu. Click the "more" button to the right of the menu to adjust the filter parameters, although the filter works well with the defaults. In some cases you might have to increase the filter gain to match the filter-off level, especially during A/B comparisons. Try it with a weak station on the AM broadcast band or ham band SSB signal.

Note that some noise filters always require their sections be enabled via the "more" panel. Otherwise simply selecting their menu entry does nothing. In particular the wdsp and LMS filters since they have independent denoiser and autonotch sections that are enabled separately (or both simultaneously).

From the CHANGE_LOG file:

v1.392,393  May 28, 2020
    Noise blankers and filters:
        Added the Michael Wild noise blanker. Not a lot of operating experience with this yet.
            It seems not to work on some noise sources compared to the standard blanker.
            A good test source is 100 kHz Loran-C in AM mode using a UK Kiwi.
            Increase the gate time (standard blanker) or impulse samples (Wild blanker) to
            account for the longer Loran-C pulses compared to the usual impulse noise.

        Fixed wdsp filter: the control sliders had no effect previously!
            Now it works quite well. You have to adjust the gain carefully to prevent overload.

        Added test pulse gain and pulse width controls. And also whether the pulse is
            applied before or after the passband filtering. The Wild blanker seems only
            effective on post-filter pulses. Probably because the filter is turning the
            pre-filter step function pulses into nicer band-limited pulses.

From the CHANGE_LOG file:

v1.391  May 23, 2020
    User interface changes:
        SAL, SAU mode passband image will only show single sideband (just like LSB, USB).
        Ctrl/alt-click on mode button toggles modes backwards (most useful with SAM modes).
        Same works with keyboard shortcuts, e.g. ctrl/alt-A toggles SAM modes backwards.
    
    Noise blankers and filters:
        Reworked the audio tab user interface to support multiple blanker/filter algorithms.
        New algorithms planned but not yet available are greyed-out in the menus.
        From Warren Pratt's wdsp package added the variable-leak LMS algorithm.
    
    Merged Howard Su's RPi changes.
        Note: RPi is not officially supported by KiwiSDR. Ask for help on the KiwiSDR forum:
            http://forum.kiwisdr.com/discussion/1986/port-kiwisdr-to-raspberrypi-3b
    
    Bug fixes:
        Audio recordings made in SAS (synchronous AM stereo) mode now work.
        Fixed problem with ITU region 2 Kiwis and shift-clicking waterfall in 75/80m band segment.
        from lazywalker: fixed problems with frequency memory and reload value when transverter offset used.